Search

Steel-concrete composite beams subjected to negative hogging moment are subject to the phenomenon of lateral stability, called lateral distortional buckling (LDB). The correct determination of the elastic critical moment, responsible for this stability phenomenon, is fundamental for the determination of the LDB ultimate moment of steel-concrete composite beams. Through the development of elastic stability analysis with the GBTul software, the elastic critical moment was determined for the situation of uniform and linear distribution of negative hogging moment. The parametric study analyzed different cross sections of I profile, the length between supports and the variation in the longitudinal reinforcement rate of the concrete slab, in total 576 models were analyzed. The results were compared with the procedures of Roik et al. (1990) and Hanswille et al. (1998) and a conservative situation was found for both procedures with differences of 26.60% and 19.88% respectively. Condition that can lead to the mistaken determination of the LDB strength, since the Roik et al. (1990) procedure is used by the Brazilian standard, ABNT NBR 8800 (2008). Therefore, it is concluded that there is a need for further studies on the subject to adapt the procedures of the Brazilian standard. [ABSTRACT FROM AUTHOR]

In prestressed concrete, due to the application of the prestressing force, the anchorages zones are subjected to high stresses. Along a stretch, called anchorage zone, the distribution of these stresses is not uniform, with transversal stress acting in the structural element. To resist the transverse stresses, it is necessary to adopt complementary reinforcement, called anchorage zone reinforcement. In this context, this paper aimed to investigate the behavior and distribution of stresses along the regularization length of prestressed elements, numerically evaluating in the Abaqus® software the influence and importance of anchorage zone reinforcement on such elements. For this purpose, four numerical models were simulated, VE, VEF-3, VEF-4 and VEF-5, with the same area of longitudinal and transversal reinforcement, differing in the fact that the VEF-3, VEF-4 and VEF-5 have, respectively, 3, 4 and 5 additional stirrups at each end of the beam. It was found that the insertion of the additional stirrups did not promote significant changes in the compression failure in the anchorage region, however it did promote relevant reductions in the failure in the traction. In addition, in the VE model, the value of the stress in the armature reached the yield strength of the steel, while in the models VEF-3, VEF-4 and VEF-5 the stresses reduced 19.48%, 56.58% and 57.96 % in relation to VE. This fact highlights the importance of anchorage zone reinforcement to assegurate the safety of unbonded post-tensioned beams. [ABSTRACT FROM AUTHOR]

Steel and concrete composite bridges and viaducts, especially in the box section, have several advantages. However, there is big discrepancy in the recommendations for calculating the effective width of the slab. For this reason, the influence of such variation on the design of compósite steel and concrete bridges and viaducts in a box section is studied. For that, 11 models were designed, varying the cross section and span, in which, considering the recommendations of the NBR 8800 (2008), AASHTO (2017), EN 1994-2-2 (2005) and those of the literature of Zhu et al. (2015) and Yuan et al. (2016), it was calculated the capacity resistant to the bending moment of the composite section and the limit distributed load for dimensioning in the Service Limit State. In the analysis, comparing the values of capacity resistant to the mean bending moment of NBR 8800 (2008) with AASHTO (2017), the first presents values 17.07% higher. In addition, NBR 8800 (2008) and EN 1994-2-2 (2005) allow shipments distributed to upper limits, on average, 14.51% and 13.18%, respectively, to those made possible by AASHTO (2017). Moreover, as the span of bridges and viaducts increases, the greater the overall variation in the resistance of the composite section. Therefore, the discrepancy between the normative recommendations has a significant influence on the design process, and it is important to carry out studies in this area in order to standardize the procedures to determine the effective width. [ABSTRACT FROM AUTHOR]